1. Field of the Invention
This invention relates to a method of manufacturing a capacitor of a memory. Specifically, this invention relates to a method of forming a capacitor insulating film over a lower electrode of a capacitor.
2. Description of the Related Art
With high integration and densification of a VLSI, the dimensions of a device have been miniaturized in recent years. With their miniaturization, the capacity of a capacitor decreases as a result of a reduction in the area of the capacitor. In order to improve this, there is known a method of forming a low-layer silicon nitride film and a Ta.sub.2 O.sub.5 film on doped polysilicon for a capacitor lower electrode as a capacitor insulating film.
The method of forming the nitride film and the Ta.sub.2 O.sub.5 will be explained below.
An interlayer insulating film is formed over a doped silicon substrate. A lower electrode corresponding to polysilicon is formed on the interlayer insulating film. A RTN (Rapid Thermal Nitrization) process is effected on the surface of the doped polysilicon in an atmosphere of NH.sub.3 at temperatures ranging from 700.degree. C. to 1000.degree. C. to thereby form a low-layer silicon nitride film. Subsequent to this formation, a Ta.sub.2 O.sub.5 film is deposited on the low-layer nitride film by an LPCVD (Low Pressure Chemical Vapor deposition) method. Annealing is effected on the Ta.sub.2 O.sub.5 film in an atmosphere of oxidation at a temperature of 600.degree. C. or more. Thus, the Ta.sub.2 O.sub.5 film is formed as a capacitor insulating film. Doped polysilicon or TiN is deposited on the capacitor insulating film by the LPCVD method and thereafter subjected to patterning. A capacitor is completed in the above-described manner.